Reagent test strips are widely used in many fields, including the fields of medicine and clinical chemistry. A reagent test strip usually has one or more reagent test areas, and each reagent test area is capable of undergoing a color change in response to contact with a liquid specimen. The liquid specimen usually contains one or more constituents, substances, or properties of interest. The presence and concentrations of these constituents of interest in the specimen are determinable by an analysis of the color changes undergone by the reagent test strip. Usually, this analysis involves a color comparison between the reagent test area or reagent test pad and a standard color or color scale, such as a color wheel. In this way, reagent test strips assist physicians in diagnosing diseases and other health problems, for example.
To satisfy the needs of the medical profession, as well as other expanding technologies, such as the brewing industry, chemical manufacturing, etc., a myriad of analytical procedures, compositions, and tools have been developed, including the so-called “dip-and-read” type reagent test devices. Regardless of whether dip-and-read test devices are used for the analysis of a biological fluid or tissue, or for the analysis of a commercial or industrial fluid or substance, the general procedure involves a reagent test device coming in contact with the sample or specimen to be tested, and manually or instrumentally analyzing the reagent test device.
Dip-and-read reagent test devices can be manufactured at relatively low cost and are very convenient for individuals to use. Consequently dip-and-read reagent test devices enjoy wide use in many analytical applications, especially in the chemical analysis of biological fluids, because of their relatively low cost, ease of usability, and speed in obtaining results. In medicine, for example, numerous physiological functions can be monitored merely by dipping a dip-and-read reagent test device into a sample of body fluid or tissue, such as urine or blood, (or by applying the sample to the reagent test device) and observing a detectable response, such as a change in color and/or a change in the amount of light reflected from, or absorbed by the test device.
Many analysis systems for reagent test devices for detecting body fluid components are capable of making quantitative, or at least semi-quantitative, measurements. Thus, by measuring the detectable response after a predetermined time, a user can obtain not only a positive indication of the presence of a particular constituent in a test sample, but also an estimate of how much of the constituent is present. Such dip-and-read reagent test devices provide physicians and laboratory technicians with a facile diagnostic tool, as well as with the ability to gauge the extent of disease or of bodily malfunction.
Illustrative of dip-and-read reagent test devices currently in use are products available from Siemens Healthcare Diagnostics Inc. under the trademark MULTISTIX, and others. Immunochemical, diagnostic, or serological test devices such as these usually include one or more carrier matrix, such as absorbent paper, having incorporated therein a particular reagent or reactant system which manifests a detectable response (e.g., a color change) in the presence of a specific test sample component or constituent. Depending on the reactant system incorporated with a particular matrix, these reagent test devices can detect the presence of substances such as glucose, ketone bodies, bilirubin, urobilinogen, occult blood, nitrite, and other substances. A specific change in the intensity of color observed within a specific time range after contacting the reagent test device with a sample is indicative of the presence of a particular constituent and/or its concentration in the sample. Some other examples of reagent test devices and reagent systems may be found in U.S. Pat. Nos. 3,123,443; 3,212,855; and 3,814,668.
Testing tools and methods have been sought in the art for economically and rapidly conducting multiple tests, especially via using automated processing. Automated analyzer systems have an advantage with respect to cost per test, test handling volumes, and/or speed of obtaining test results or other information over manual testing.
A recent development is the introduction of multiple-profile reagent cards and multiple-profile reagent card automated analyzers. Multiple-profile reagent cards are essentially card-shaped test devices which include a substrate and multiple reagent-impregnated pads (or matrices), and/or blank test pads (also known as color pads) without reagents, positioned onto the substrate, for simultaneously or sequentially performing multiple analyses of analytes, such as the one described in U.S. Pat. No. 4,526,753, for example, the entire disclosure of which is hereby expressly incorporated herein by reference.
Multiple-profile reagent cards result in an efficient, economical, rapid, and convenient way of performing automated analyses. Automated analyzers configured to use multiple-profile reagent cards typically take a multiple-profile reagent card, such as from a storage drawer, or a cassette, and advance the multiple-profile reagent card through the analyzer over a travel surface via a card moving mechanism. The card moving mechanism may be a conveyor belt, a ratchet mechanism, a sliding ramp, or a card-gripping or pulling mechanism, for example. As the multiple-profile reagent card is moved or travels along the travel surface, one or more sample dispensers (e.g., manual or automatic pipette or pipette boom) may deposit or dispense one or more samples or reagents onto one or more of the reagent pads. Next, the multiple-profile reagent card may be analyzed (e.g., manually or automatically) to gauge the test result, such as via an optical imaging system, a microscope, or a spectrometer, for example. Finally, the used reagent card is removed from the analyzer, and is discarded or disposed of in an appropriate manner, such as a waste receptacle.
However, in some instances the detectable response of the reagent pad and the specimen results in one or more false positive results indicating the detection of the constituent, such as an analyte, in the specimen. To that end, a need exists in the prior art for systems and methods to reduce the occurrence of false positive results. It is to such analytical detection and verification systems and methods that the inventive concepts disclosed herein are directed.